1. Field of the Invention
The present invention relates to a safety-belt retractor for an automotive vehicle or other vehicles. More particularly, the present invention relates to a locking device of the safety-belt retractor which is operative to lock the extraction or protraction of the safety-belt when the vehicle is suddenly decelerated and thereby to protect a user or wearer from crashing onto the vehicle floor.
2. Description of the Prior Art
As is well-known, there have been provided various safety-belt arrangements in automotive vehicles or other vehicles for protecting persons seated within the vehicle, and wearing the safety-belt, from danger caused by their inertia when the vehicle is suddenly decelerated. In the present specification, the change of the vehicle velocity refers generally slowing down of the velocity, wherein the inertia of the persons seated in the vehicle forces them to move frontwardly and thereby into opposed vehicular parts. While, when the vehicle velocity is suddenly accelerated, the persons are forced backwardly and thus forced against their seat. Therefore, it is unnecessary to restrain the user from backward movement against the seat.
In order to protect a person from danger of crashing onto the opposed vehicular interior, various safety-belt arrangements have been used to restrain the person in the seat, when the vehicle is suddenly decelerated. The safety-belt arrangement generally has a rotatable reel, upon which a safety-belt is wound, to allow automatic extraction and retraction of a belt. The reel is biased by a resilient member in a direction for retracting or rewinding the belt thereon. When the vehicle velocity is suddenly changed, the inertia to which the person is subjected to cause the person to move frontwardly so as to cause extraction of the belt against the force of the resilient member. Such a safety-belt device has been necessarily provided with a locking device generally comprising at least a pair of ratchet wheels and a locking element for locking the extraction of the belt so that the belt may restrain the person on the seat.
There have been provided various contructions of means for operating the locking device having the locking element. Generally, the operation means becomes operative when there is a change of vehicle velocity. In this type of the operation means, a pendulum assembly has been employed which is operative in response to inertia caused by sudden change of vehicle velocity. When the vehicle is normally driven, the pendulum assembly is in a normal position in which the vertical axis of the pendulum assembly is directed perpendicularly. When the vehicle is suddenly decelerated and the vehicle velocity is thus suddenly changed, the weight element of the pendulum assembly is subjected to an inertia thereby drawing the same backwardly so as to tilt the axis of the assembly. The tilting of the pendulum assembly may cause operation of the locking device to lock the safety-belt reel so as not to extract. The pendulum assembly operates the locking device in such a manner that a top of the assembly located in a lateral position with respect to the vertical axis is tilted and thereby a portion thereof rises to push up the locking device.
During the retracting operation of the locking device, there has occasionally arisen a serious problem in that the locking device cannot be efficiently interlocked with the ratchet wheel, and thereby possibly results in extraction of the safety-belt. This has been caused by the contact of the locking element with the top of a tooth of the ratchet wheel subjecting the locking element to a reaction, and is thereby deflected or kicked off of the ratchet wheel, that may result in disengagement of the locking element and ratchet wheel.
In the prior art, there are various improved constructions of the locking mechanism to ensure the interlocking of the locking device and the ratchet wheel. In one known arrangement, there is provided a plurality of inertia sensing elements or locking elements so as to reduce the probability of accidental disengagement occurring when the vehicle is suddenly decelerated. Further, in another conventional construction, the safety-belt retractor has two interconnected locking members so that one of the members may operate to ensure engagement of the ratchet wheel and the other locking member. In such constructions, there are naturally required one more sets of ratchet wheels and locking members and an inertia sensing member which causes increased weight as well as costs and to cause difficulties in assembling.
One of the typical construction of the improved safety-belt retractor is disclosed in U.S. Pat. No. 4,090,678 issued on 23rd May, 1978 to Chusaka YAMANASHI and assigned to FUJI KIKO K.K., assignee of the present invention. In the Yamanashi patent, particularly the second embodiment with reference to FIGS. 5 and 6 thereof, there is disclosed and illustrated a safety-belt retractor having first and second ratchet wheels. The second ratchet wheel may be made of relatively soft material with respect to the first ratchet wheel, such as plastic. The second ratchet wheel has the same numbers to teeth as that of the first ratchet wheel and has a diameter slightly larger than that of the first ratchet wheel. The second ratchet wheel is rotatably secured on an axle adjacent to the first ratchet wheel in a coaxial relationship. The second ratchet wheel is engaged with a short leg portion of a substantially L-shaped locking element which has an end engaged to the first ratchet wheel. Employment of the second ratchet wheel of comparably soft material is intended to ensure engagement between the teeth of the ratchet wheel and the short leg of locking element, and thus to ensure meshing the end of locking element to the first ratchet wheel.
Another type of improved locking mechanism for safety-belt retractor has been disclosed in U.K. Pat. No. 1,356,257, granted on July 20th, 1971, to KANGOL MAGNET LIMITED. In the U.K. Pat. No. 1,356,257, there has been disclosed an inertia reel device comprising a rotatable spindle from which a vehicle safety belt can be unwound against the tension of a rewind spring, first and second ratchet wheels rotatable with the spindle, and first and second pawl member co-operable respectively with the first and second ratchet wheels, the first pawl member being movable by an inertia sensing device from a first position of disengagement from the first ratchet wheel to a second position of engagement therewith, and from the second position to a third position by rotation of the spindle in the belt unwinding direction, the second pawl member being arranged to be moved, on the movement of the first pawl member from the second to the third position thereof, from a first position of disengagement from the second ratchet wheel to a second position of engagement therewith to prevent further rotation of the spindle in the belt unwinding direction, and the first pawl member being mounted on a movable intermediate member for movement thereon between the first and second position and for movement therewith between the second and third position.
However such constructions of safety-belt retractor are expected to improve reliability for retracting operation when the vehicle has been suddenly decelerated, it will be easily understood that they require a number of additional parts which increase weight as well as costs therefor and cause assembling difficulties.
A further improved construction has been disclosed in British Pat. No. 1,466,458 to the American Safety Equipment Corporation, which is directed to an energy storing safety belt retractor comprising a vehicle inertia responsive means on the retractor for sensing changes in the inertia of the vehicle and energy storing means in force-transmitting relationship between the vehicle inertia responsive means and a lock bar for urging the lock bar toward locking engagement with the ratchet wheel. British Pat. No. 1,466,548 teaches various embodiments having vehicle inertia responsive means including elastic members for accumulating force for urging the lock bar into locking engagement with the ratchet wheel. In the illustrated constructions, if the lock bar collides with the top of the ratchet wheel, and is thereby kicked off, the force for urging the locking bar toward the ratchet wheel is accumulated in the elastic member for assurance of the interengagement between the lock bar and the ratchet wheel. However, due to the relationship between the metallic supporting plate and the actuator means including the pendulum member, noise will be generated by vehicle vibration transmitted thereto. In response to vehicle vibration, the pendulum member may move the actuator in any direction with respect to the supporting member. This causes a collision between the supporting plate and the actuator and thereby generates the noise. Further, since the actuator always contacts the supporting plate, it is subject to friction between the edge of the opening formed in the supporting plate. This will possibly cause wear of the actuator. For reducing wear of the actuator, it has been required to make the inner periphery of the opening of the supporting plate smooth enough to minimize the friction between the actuator and the supporting plate. For smoothing the inner periphery of the opening accurate processing of the surface is required which necessarily increases the cost thereof.
Additionally, in the shown construction, since the stem for connecting the actuator and the pendulum member are made of different materials from the remainder of the construction and is formed separately, the pendulum and actuator assembly will be assembled in such a manner that, at first, one of the actuator or the pendulum is secured to one end of the stem, the stem is passed through the opening of the supporting plate and then the remaining one of the pendulum member or the actuator is secured to the other end of the stem. This necessarily requires a fixing process on the both ends of the step to fixedly secure the actuator and the pendulum member. Generally, the end of the stem is clamped to fixedly secure the pendulum and the actuator to vary the length of the stem and therefore it is quite difficult to assure the constant length of stem.
The present invention is to improve the above-mentioned disadvantages or defects in the prior art and to improve a safety-belt retractor capable of reducing the manufacturing cost and simplify the assembling operation.